ABCs -> infix syntax for isinstance() ?

[Boris Borcic]

Terry Reedy wrote:
> Boris Borcic wrote:
...
>>
>> - allowing containment tests, ie "x in Number" to invoke isinstance() 
>> in the background when the container is of type <type>. My brain is 
>> too muddled by flu at the moment, to see whether Guido's fabled time 
>> machine allowed him to already provide all the necessities in py26.
>> Any takers ?
> 
> I believe this could be done by adding a __contains__ method to type.
> (It does not have one now).  Then x in X should work for all classes 
> that are instances of type or a subclass thereof.

Can this be done short of patching the source and recompiling (eg, with ctypes 
perhaps) ?

Cheers, BB